The invention relates to cleaning pipes and particularly to cleaning inner surfaces of used sewage pipes.
Instead of uncovering the pipes and replacing them with new ones, sewage pipes at the end of their life cycle can often be renovated without opening structures. Renovation requires that the existing pipe be carefully cleaned to remove blockages, dirt and rust before a coating or a renovation lining to be installed in the renovation can be installed in an old pipe. Pipes to be renovated are typically several decades old and there may be significant damages in them, such as cracks, splits, missing pieces and poor joints. In some cases, even the entire pipe bottom has worn off and in the soil under the pipe, a small ditch has been formed where sewage waste is flowing. Despite damages, renovation can be successfully carried out by using a renovation lining but the damages in the pipe make cleaning difficult.
Finnish utility model publication FI10735 discloses a technique for cleaning the inner surface of sewage pipe systems, in use at least since the 1940s. The publication discloses a cleaning device consisting of chains the loops of which are provided with welded or soldered hard metal blades. The chains are rotated in the pipe system, whereby the hard metal blades grind the inner surface of the pipe.
A problem with the above arrangement is that chains get stuck at the damaged points of the pipe when the hard metal blades in the chain push into cracks, joints or the like damaged points. It is difficult to remove a stuck chain without breaking the pipe more, particularly when the chain gets stuck in a portion after several bends. Even if the chain did not get stuck when a larger piece is missing from a pipe, the hard metal blades in the chain have sharp edges and they are protruding, so they hit the sharp edge of a larger opening with force, which makes the rotation of the chain stop and may cause the chain-rotating cable to break. In addition to the operational problems, it is laborious to manufacture above-described chains as, in practice, they must be welded manually, whereby the manufacture is slow and labour-intensive. Repairing a chain due to the wearing of hard metal blades is almost as laborious as making a completely new chain, so it is not profitable.
In cleaning the inside of sewage pipes, high-pressure injection of water can also be used but the cleaning result is not perfect. Rust removal, in particular, is difficult by injecting water. Furthermore, in the case of larger damaged points, for instance when the pipe bottom has worn off, the injected water runs out of the damaged point, causing further damage.
As a third alternative, a rotatable spindle has been used for cleaning the inside of pipes, the spindle having abrasive, flexible strips or flexible strips provided with blades. A problem with abrasive strips is that they get clogged fast, whereby their abrasive properties disappear and the strip needs to be replaced with a new one. Blades used in strips solve the clogging problem but they have problems with damaged points, similar to those of chains. The blade in a strip may get stuck in a crack, pipe joint or cleft, and when a larger piece is missing from the pipe, the fastening point of the blade hits the edge of the damaged point and breaks the blade, strip, cable or pipe.